Yarn sizing process



Patented Apr. 7, 1942 UNITED STATES PATENT OFFICE 2,273,902 rank. srzmc mocess Edgar W. SpanagelfWVilmington, DeL, assignor to E. I. du Pont de Nemours & Company, Wilmington, D'eL, a corporation of Delaware bio Drawing. Application December 13, 1940,

' Serial N0. 369,951

g; Claims.

. restricted to the application of an adhesive coating to a yarn to protect the many filaments thereof during the formation of a textile material from the yarn and in the course of subsequent handling of the textile. The term sizing does not refer to the application of other finishes, dressings, oil coatings, and the like.

The present invention is directed to the sizing of the yarn on-the-run," that is, as the yarn passes from one package to another. The sizing of yarn in package form, or skein form, is generally considered to be inferior due to yarn degradation, waste of size, and non-uniformity of application. Furthermore, in skein sizing, it isdlfficult to apply a suflicient percentage of size to give adequate snag protection to the yarn, especially in low denier yarns.

Heretofore, in the sizing of yarn on-the-run, it has been considered necessary to dry the yarn before the latter is wound on a supporting means to form a yarn package. For a considerable period of time, it was found that synthetic linear polyamide yarn sized in the above-mentioned conventional manner was quite unsuitable for use in textile operations in that the fabrics, knitted according to such a method, had an impractical low resistance to snagging during fabrication and it was impossible to obtain an economic propor tion of first grade fabrics. Additionally, considerable quantities of the size accumulated on the knitting machine parts (Snappers, carrier tubes, needles and sinkers).. The deposited size became hard and abrasive. Thus, when the yarn passed over these deposits at the fast rate of operation of the machine, the delicate filaments would become snagged, abraded and torn. The

yarn would break and cause press-oils, production would be stopped, and the machine would have to be taken out of service until an expensive clean-up procedure was completed.

'It is therefore an object of the present invention to provide a satisfactory process for the application of a size to a synthetic linear polyamide yarn.

It is another object of this invention to provide a satisfactory process for applying size to a synthetic linear polyamide yarn on-the-run.

It is still another object of the present invention to provide a satisfactory process of sizing on-the-run, a synthetic linear polyamide yarn so that the yarn will subsequently be suitable for use in all textile operations.

Other objects of the invention will appear hereinafter.

The objects of the present invention are accomplished, in general, by a process in which an aqueous size composition, after having been applied to the yarn, is made to retain at least 50% water (based on the weight of the solids in the size composition) for a period of at least one minute after the size application. The above-named percentage of water and period of time is considered critical on the basis of a satisfactorily sized yarn. It will be obvious to one skilled in the art that this is a complete reversal of previously known standard practice. Heretofore, sizes have been applied to yarns from quick drying size compositions or by processes in which the size was immediately dried on the yarn after application.

Although there are numerous methods of carrying out the process of the present invention, the preferred method comprises the sizing of the yarn and winding of the same on a bobbin, or other support, while it is still wet.

The following examples are given to illustrate preferred methods of applying sizes to synthetic linear polyamide yarns. The details set forth in the examples are not, however, to be considered as limitative of the invention. The percentages set forth in the examples, in the absence of anything to the contrary, designate percentages by weight.

Example I Polyhexamethylene adipamide yarn of 30- denier, ill-filament, 30-turn Z twist is sized at 50% relative humidity and F. with an aqueous size containing:

Per cent Partially hydrolyzed polyvinyl acetate.-... 8 Boric acid (based on the partially hydrolyzed polyvinyl acetate) 21.5

The yarn is drawn ofi a supply pirn and then passes over a size roller which rotates in a trough The partially hydrolyzed polyvinyl acetnle is of saponiflcatlon l\ o. :10 and is within the viscosity range of 400400 seconds (Universal Saybolt at 78 1'.

' in 14.5% solution in water).

containing the size solution. The yarn is then wound up on a bobbin while it is still wet. The bobbin containing the sized yarn is then allowed to stand in a room of the above temperature and relative humidity for 16 hours at which time it is dry and ready for further textile operations. At the end of one minute after the application of the size, the size associated with the yarn contains 500% water based on the solid components of the size. The sized yarn, after drying has applied to it 4% of size based on'the weight of the yarn. Yarn sized by this method can be knit. without difdculty on a high-speed full-fashioned knitting machine. The size adheres tenaciously to the yarn without the formation of deposits on the needles and sinkers of the machine. A stocking blank made from yarn sized in this way is highly satisfactory in its resistance to snagging. High snag resistance is essential for the manufacture of a suflicient proportion of first grade fabrics to make economical production possible;

Example II Polyhexamethylene adipamide yarn of 70'- denier, 23-fllament, 1 /2 tum "Z twist is sized, using the same method and apparatus as were used in Example I. The aqueous size composition contains:

, Percent Partially hydrolyzed polyvinyl acetate (same as in Example I) 6 Boric acid (based on the partially hydrolyzed polyvinyl acetate) 21.5 Polyethylene glycol of an average molecular weight of 4000 (based on the partially hydrolyzed polyvinyl acetate) 15 At the end of one minute after application of the size, the size associated with the yarn contains 300% water based on the solid components of the size.

The quantity of size applied to the yarn when dry is 1.5%, based on the weight of the yarn. After drying the yarn is twisted to 10 turns per inch. The sized yarn and the fabric knit from it exhibit the same highly satisfactory properties as the high twist 30-denier yarn of Example I. The inclusion of the polyethylene glycol tends to make the sized yarn more pliable and to give more satisfactory stitch formation.

Example III A 30-denier, IO-iilament, 1 /2 turn Z twist polyhexamethylene adipamide yarn is sized with the same apparatus as was described in Example I. The size solution and operating conditions are the same as those employed in Example I. At the end of one minute after the application of the size, the size associated with the yarn contains 700% water based on the solid components of the size. The amount of size applied to the yarn when dry is 4%, based on the weight of the yarn. The yarn is then twisted to 30 turns per inch, and is then knit to form a full-fashioned hosiery fabric,

This example is included to show the use of this process in the sizing of low denier, low twist yarn. This yarn, as well as the fabric knit therefrom, has equally good properties as the yarn of the preceding examples.

Example IV Polyhexamethylene adipamide yarn of 30- denier, lo-i'llament, 1 /2 turn Z twist is sized in a modified warp sizer with the yarn traveling at a rate of 30 feet per minute. The sizing composition is an aqueous dispersion containing:

- Per cent Partially hydrolyzed polyvinyl acetate (as in Example-I) Boric acid (based on the weight of the partially hydrolyzed polyvinyl acetate) 22 Polyethylene glycol (as in Example II, based on the partially hydrolyzed polyvinyl acetate) 10 The yarn is given an air travel of 30 feet at a temperature of F. and a relative humidity of At the end of one minute, that is, at the end of the air travel, the size associated with the yarn contains about water based on the solid components of the size. The yarn is then passed through a drying oven having a length of 14 feet and having a temperature of 212 F. Upon leaving the oven, the yarn is dry, and is wound on spools. This yarn is then twisted to 30 turns per inch and the twist is set by maintaining it in an oven for 1 /2 hours at 170 F. dry bulb and F. wet bulb. The amount of size applied to the yarn is 4.4%, based on the weight of the yarn. This yarn. when knit in a fullfashioned machine, gives excellent running properties.

When size is applied on a warp sizer under the same conditions as stated above, except that the period of air travel above referred to is omitted and the size is dried immediately after application, that is, in accordance with the conventional warp sizing procedure, the size will have extremely poor running qualities, depositing upon the knitting needles and sinkers of the knitting machine, and the knit fabric will have such a low snag resistance that it is little better than unsized yarn.

Although in most of the examples a preference has been shown for a sizing composition which contains about 900% water, based on the solids content of the size, and for a process in which the yarn was wound up wet and brought to dryness over a period of 16 hours, itis to be understood that the concentration of the size composition may be varied between wide limits, due recognition of course being taken of the solubility of the solids and of the requirement for applying to the yarn a predetermined quantity of solids. Similarly, the time of 16 hours was that dictated by the practical circumstances of production. For the purposes of this invention, the drying of the yarn must take place at a rate sufilciently slow that after a period of one minute after application of the size, the size composition on the yarn will contain at least 50% water, based on the weight of the solids in the size composition.

' The drying can, of course, be carried out at a slower rate.

While the invention in its preferred form involves a procedure in which the yarn is sized anc wound on a support while it is still wet, the process. of this invention can be successfully carried out, as indicated above, if the yarn is given a-suitable period of air travel before drying. This period of air travel may take place in some form of tunnel which has the desired conditions of temperature and humidity such as will preclude the quick drying of the yarn. This period of air travel may conveniently be carried out by running the yarn on some form of thread-storing, thread-advancing reel contained within an area of the proper conditions of temperature" and humidity to assure that the size applied to the yarn contains at least 50% moisture based on the solids for a period of at least one minute.

In connection with sizing to a support while the yarn is still wet, it is preferred that the sized yarn be maintained at a relative humidity of about 50% and a temperature of about 80 F.; however, considerable deviation from these figures is obviously possible. The preferred range is between 30% and 75% relative humidity and between 65 and 100 F. Although the above ranges are preferred, as above pointed out, it is only necessary that the yarn be dried at'a sufiiciently low rate that after a period of one minute the size contained on the yarn will contain at least 50% water based on the weight of the solids in the sized composition.

The size composition may be applied to the yarn in any desired manner; for example, the size may be applied by means of a size applying roller, or the size may be applied by immersing the yarn in a bath as the yarn passes from one package to another. Alternatively, the sizing composition may be applied to the yarn by spraying, brushing or in any other desired manner. If the size is applied by means of a size applying roller, the roller may be of any desired size and the yarn may contact the roll over any desired length of its peripheral surface. Naturally, if the speed of the size roll is increased, the quantity of the size applied to the yarn will correspondingly be increased. Fur thermore, the yarn may be subjected to any desired tension while the size is being applied thereto.

The term synthetic linear polyamide, as used through the specification and claims, is intended to refer specifically to the fiber-forming material described and claimed in United States Letters Patent Nos. 2,071,250, 2,130,523, and 2,130,948. The polymers there described are high molecular weight products which'are generally crystalline in structure and which are capable of being cold drawn into fibers showing, by characteristic X-ray patterns, molecular orientation along the fiber axis. For the best fiber-forming properties, the polymerization reaction should be continued until the intrinsic viscosity is at least 0.4. Generally speaking, these synthetic linear polyamides comprise thereaction product of a polyamide-forming composition in which the molecules are bi-functional and contain two amide-forming groups, each of which is complementary to an amide-forming group in other molecules in said composition.

These polyamides-as defined above or as otherwise identified hereinafter can be obtained, for example, by self polymerization of mono-aminomonocarboxylic acids, or by reacting a diamine with a dicarboxylic acid in substantially equimolecular amounts, it being understood that reference herein to the amino acids and dicarboxylic acids is intended to include the equivalent amide-forming derivatives of the amino acids and of the dicarboxylic acids. These linear polya-mides include also polymers obtained by admixture of other linear polymer-forming reactants, as for instance glycols in the case of polyester amides, with the mentioned polyamideforming reactants. In either instance the amide group is an integral part of the main chain of atoms in which, in the case of the preferred fiber-forming polyamides, the average number of atoms separating the amide group is at least two.

The term synthetic linearpolymer," is intended to refer, in addition to the synthetic linear polyami'des, to the fiber-forming synthetic lin'ear polyesters, polyethers, polyacetals, vinyl polymers, and ethylene polymers, as well as fiberforming interpolymers of the above-mentioned synthetic linear polymers.

The present invention relates to the use of all aqueous sizing compositions which are suitable for use in sizing synthetic linear polymers and particularly synthetic linear polyamides- Exceptionally desirable results have been obtained by the use of sizes of the type described in Spanagel application Serial No. 357,757,.filed September 21, 1940; Spanagel and Maxwell application Serial No. 357,756; filed September 21, 1940; Strain application Serial No. 357,755, filed September 21, 1940; and Spanagel application Serial No. 237,789, filed October 29, 193& Other aqueous sizing compositions include glue sizes, casein sizes, gelatine sizes, methacrylate interpolymer sizes, water-soluble methyl cellulose sizes, starch derivative sizes and mixtures of suc sizes with the sizes referred to in the applications specifically enumerated above.

Yarn sized in accordance with the present invention will be particularly satisfactory in the knitting of ladies sheer hosiery on full-fashioned hosiery knitting machines. Thus, by the process of this invention, it is commercially possible to apply a sizing composition from an aqueous dispersion to an extremely fine and delicate low denier yarn such as is required for the sheerest of full-fashioned hosiery. This process is particularly applicable to the sizing of yarns of 50 denier or less. The sized yarns produced in accordance with the present invention may be moistened, as is customary in the full-fashioned knitting art, and can be subjected to the rigors of the high speed knitting machine.

When stockings are made from yarn sized according to this process, the percentage of first class stockings produced is markedly higher than when yarn sized according to the prior art practice is used. The stocking blank knitted from yarn sized according to this process has the property of great resistance to snagging. The size does not accumulate on the knitting machine. parts even when moistened, for example, by passing the yarn through an aqueous bath immediately prior to the knitting operation.

Although the sizing of yarn in accordance with the present invention has particular utility in the sizing of yarn to be used in the production of ladies sheer, full-fashioned hosiery, it will be readilyapparent that yarns sized in accordance with the process of the present invention will also be satisfactory in the production of textiles by weaving or other textile operations. The

excellent protection to the yarn produced by the process of this invention will render the sized yarn applicable to all other textile processes.

While it was previously thought that the dimculties of sizing synthetic linear polymer yarn would make it necessary to resort to skein sizing and that it would not be possible to take advantage of the more modern and efllcient onthe-run methods, such proved not to be the case. By a simple but critical change in the known procedure of sizing on-the-run, the difliculties disappear and wholly satisfactory results are achieved, with the additional advantage of even greater economy as noted above. The textile art is replete with examples of various methods for the drying of yarn after sizing, such that a skilled workman in this art feels that the essential of a satisfactory sizing technique drying of the sized yarn. never occur to one skilled in the art so to fly in the face of established textile principles in attempting to satisfactorily size a new yam. However, it proved that known practices were unavailing in solving the problem, but that the opposite procedure from the standard practice solved it.

Since, in the preferred practice of the process of this invention, the yarn .is wound up while still in a wet and tacky condition, it would be expected that subsequent unwinding would be fraught with that the adjacent turnsof yarn would stick to one another, and that yarn and filament breakage would be encountered in attempting to unwind. Surprisingly and contrary to expectations, bobbins sized according to this process are capable of being unwound over end perfectly safely and without the difliculities of breakage and uneven tension that might be expected.

Since it is obvious that many changes and modifications can be made in the details above described without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited to the above described details except as set' forth in the appended claims.

I claim:

1. The process which comprises sizing, on-thecomprises a rapid difficulty. It might be expected- It would certainly slow that the sizing run, a yarn composed of filaments of a synthetic linear polymer with an aqueous sizing composition, and drying said yarn at a rate sufficiently composition associated with the yarn one minute after application thereof contains at least 50% water, based on the weight of the solids in the composition.

2. The process defined in claim 1 in which the synthetic linear polymer yarn is a synthetic linear polyamide.

3. The process defined in claim 1 in which the synthetic linear polymer yarn is a synthetic linear vinyl polymer.

4. The process defined in claim 1 in which the synthetic linear polymer yarn is a synthetic linear interpolymer.

' 5. The process defined in claim 1 in which the aqueous size comprises a partially hydrolyzed polyvinyl acetate.

6. Theprocess which comprises sizing, on-therun, a yarn composed of filaments of a synthetic linear polymer with an aqueous sizing com-position, winding the yarn on a support to form a yarn package while the yarn is still wet, and delaying the drying of said yarn sumciently that sizing composition associated with the yarn one minute after application thereof contains at least 50% water, based on the weight of the solids in the composition.

- EDGAR W. SPANAGEL. 

